The present invention relates to an intake system for use in a V-shaped engine.
A conventional intake system for use in a V-shaped engine is disclosed, for example, in Japanese Patent Application Laid-open No. 159725/87.
In the conventional systems, both the intake pipe assemblies and the surge tank are formed from a metal such as a cast iron or an aluminum alloy. This is one factor which increases the weight of the engine. Therefore, it was conceived that the intake pipe assemblies and the surge tank would be formed from a synthetic resin, thereby reducing the weight of the engine. However, the problem arises that if the intake pipe assemblies and the surge tank are merely made of synthetic resin, stress is concentrated on the flange-coupled portions of the intake pipe assemblies and the surge tank, as a result of vibration and thermal elongation from the cylinder head sides. This results in the difficulty of assuring the sealability between the intake pipe assemblies and the surge tank. Thus, when the flanges of the intake pipe assemblies and the surge tank made of the synthetic resin are coupled directly to each other, it is difficult to maintain enough coupling force to assure the sealability against the vibration and the thermal influence from the cylinder head sides.